códecs

Codecs, short for coder-decoder, are algorithms and the corresponding software or hardware used to compress and decompress digital media data. They enable efficient storage, transmission, and playback of audio and video by reducing redundancy while preserving an acceptable level of quality. A codec is typically used with a container format that holds the encoded data and metadata; the container does not define the compression method but provides a structure for multiplexing streams.

Codecs are categorized by whether they are lossless or lossy. Lossless codecs reproduce the original signal exactly, at larger file sizes (examples: FLAC for audio, FFV1 for video). Lossy codecs discard some information to achieve higher compression (examples: MP3 and AAC for audio; H.264/AVC, HEVC, VP9, AV1 for video). Modern codecs often use perceptual models to prioritize information most important to the human senses.

An encoder compresses media into a bitstream, and a decoder decompresses it for playback. In practice, software and hardware devices implement both ends of the pair, and pipelines may include multiple codecs and containers in sequence.

Licensing and openness influence adoption. Some codecs are protected by patents and require licensing (for example, H.264/AVC and HEVC), while others are designed to be royalty-free or openly developed (such as AV1 and Opus).

Codecs underpin many current media applications, including streaming services, video conferencing, broadcasting, and archival storage. Ongoing work focuses on improving efficiency, latency, and support across devices and networks.